Zollinger-Ellison (ZE) syndrome is a rare disease of the gastrointestinal tract. It is characterised by severe recurrent peptic ulcers in the stomach, and/or the upper portion of the small intestine. The ulcers are caused by a greatly increased amount of stomach acid due to high levels of gastrin, the that stimulates stomach acid production. In ZE, high gastrin levels are caused by gastrin-producing called gastrinomas, which usually form in the duodenum but can be found in the pancreas and rarely in other parts of the body. More than half of them are and can to other parts of the body, such as the liver. The tumours must be removed surgically, and sometimes total removal of the stomach is necessary to control the acid production.